1. Field of the Invention
This disclosure relates to the field of hydrocarbon reformation. In particular to the use of supercritical water to reform diesel fuel and to use supercritical water to obtain hydrogen.
2. Description of the Related Art
There is a desire in America and around the world to utilize so called clean power sources. One of the technologies that has been making a particular impression in clean power is the so-called “fuel cell” which produces electricity by the electrochemical reaction of an oxidizer and a fuel (generally hydrogen gas). While the process is similar in many ways to a battery, fuel cells have the advantage that they do not run down or require recharging, so long as there is fuel and oxidant, there is electricity.
The operation of a fuel cell is relatively straight forward. Protons flow from the fuel electrode (anode) through an ion-conducting membrane to an oxidant electrode (cathode) and combine with oxygen to form water. The electrons in turn flow from the anode to the cathode, through an external electric circuit, to create electricity. As the electricity is created through the chemical combination, there is no combustion and, therefore, the associated by-products of combustion are eliminated.
Fuel cells have drawn particular interest in automobile and vehicle power, but are useable for any type of technology where electricity can be used as power. In particular, the fuel cell may replace conventional chemical batteries or even conventional electric power plants. The fuel cell is of particular interest because it can operate at efficiencies two to three times that of the internal combustion engine, and it requires no moving parts. Further, the fuel cell operates “clean” since the only outputs of its process (presuming hydrogen is used as fuel) are heat, electricity, and water.
The biggest hurdle to the fuel cell concept, particularly in vehicle use, is to obtain hydrogen in sufficient quantities and at reasonable cost to make the fuel cell economically competitive. Further, in order to switch vehicles to fuel cell power, it is necessary for there to be infrastructure to distribute hydrogen to provide the hydrogen fuel to the fuel cells. Because of the lack of infrastructure to distribute hydrogen to consumers, especially when compared to existing infrastructure to distribute fossil fuels, many of the proposals for hydrogen generation reform existing automobile fuels into hydrogen. Further, other consumers, such as the military, are interested in being able to obtain hydrogen as fuel at remote locations. Many of these consumers also already rely on internal combustion engine power sources and already have extensive infrastructure and support structure dedicated to distributing fossil fuels.
Reforming is preferable because it allows for existing fossil fuel distribution infrastructure to be converted over time to a hydrogen distribution infrastructure, without inconvenience to first adopters of hydrogen technology, by allowing hydrogen to be obtained at conventional sources where fossil fuels are already available. Because of the need for infrastructure to be available to lead to technology adoption, some technologies for producing hydrogen simply require too specialized of materials and transportation infrastructure to be utilized efficiently at this time.
Reforming technologies allow for hydrogen to be generated wherever there are already fossil fuel sources present by reforming the fossil fuel into hydrogen. For instance, hydrogen may be formed at the refinery and distributed, or, if the reformer equipment is sufficiently small, a reformer may be placed at a conventional service station to reform automobile fuels into hydrogen on demand. If the reformer is small enough, it may even be used on-board an automobile.
Some of the most well known types of fuel reforming systems are steam reforming, partial oxidation and Autothermal reforming (ATR) (which is essentially a process using both steam reforming and partial oxidation together to eliminate inefficiencies). The problems with ATR reformers are that they require a very high temperature (850° C. or higher) and an expensive catalyst such as platinum or nickel to be effective. Further, the catalyst reactivity normally drops very rapidly as the process continues due to poisoning of the catalyst through impurities (such as sulfurous compounds or carbonyls) formed in the process unless expensive fuel prefiltering processes are used. Therefore, ATR technologies may be impracticable for use without significant safety, filtering, and power requirements. These requirements can, in turn, render the technology ineffective for use with existing fossil fuel infrastructure.